Author Topic: no success etching in greyscale  (Read 9740 times)

dindunuffin

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Re: no success etching in greyscale
« Reply #15 on: May 22, 2016, 09:55:57 AM »
I will do some experimentation with dithering.  I've ran more greyscale tests, and I've gotten it all the way down to a power level of 28, and its still black & white, although I can get a third shade of "not quite black".

From experience, do you think replacing the board may be able to get true greyscale?  Or is there a possible limitation within the laser itself, i.e. the laser control board? 

Zax

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Re: no success etching in greyscale
« Reply #16 on: May 22, 2016, 10:26:32 AM »
I believe it's the current driver in the laser module so switching Eleks boards won't help (but I could be wrong).

My laser isn't linear either, below 50 it is unreliable (at around 30 it flickers and then comes on >50) and at 255 it is significantly more powerful. Between 50 and 250 it does a reasonable job of being linear.

I just tested my machine using an L1, L2 and L6. The response was the same on all boards.

BritVic

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Re: no success etching in greyscale
« Reply #17 on: May 22, 2016, 10:53:37 AM »
I believe it's the current driver in the laser module so switching Eleks boards won't help (but I could be wrong).

My laser isn't linear either, below 50 it is unreliable (at around 30 it flickers and then comes on >50) and at 255 it is significantly more powerful. Between 50 and 250 it does a reasonable job of being linear.

I just tested my machine using an L1, L2 and L6. The response was the same on all boards.

I get exactly the same...unreliable below 50

Zax

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Re: no success etching in greyscale
« Reply #18 on: May 22, 2016, 11:17:48 AM »
I guess I should have tested it with LaserInk firmware, crap, that means I have to connect up each board again and see if it makes any difference.

The higher pulsing frequency (7.8kHz) may provide a smoother response vs. the 1kHz from J-Tech (designed for a TTL input).

ROSS

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Re: no success etching in greyscale
« Reply #19 on: May 22, 2016, 11:57:54 AM »
Thanks for the explanation.   Now its clear.
.
Lasers are wonderful machines..not ONLY  can they cut a finger off BUT  they can also cauterise it at the same time.....

SAFETY -  IS NO ACCIDENT

dindunuffin

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Re: no success etching in greyscale
« Reply #20 on: May 22, 2016, 02:14:35 PM »
I've been using the LaserIink firmware, after you suggested it, and I really can't tell any difference.  I've been trying to get dithering to work, but no cigar.  I'm still getting just black and white.  I've run speeds from 1000-3000 and power levels from 255 down to 160, with varying levels of complete failure.   It looks like I'm going to be very happy just doing B&W etching. 

What is it they used to say on Hee Haw?
 
Gloom, despair, and agony on me
Deep, dark depression, excessive misery
If it weren't for bad luck, I'd have no luck at all
Gloom, despair, and agony on me

Do you think if I take the laser off and throw it against the damn wall it would help any?  Other than make me feel better.

Zax

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Re: no success etching in greyscale
« Reply #21 on: May 22, 2016, 02:44:32 PM »
I just got finished testing LaserInk, and have to agree with you. The difference was negligible.

So I did notice that the constant current driver has a T+/T- input, so wondering if that's for TTL. I'll probably blow it up trying, but that's OK since I will just order one of those external drivers that has TTL built-in. Making smoke is what I do, sometimes from the laser, other times from the electronics - but it's more satisfying than throwing it against the wall (marginally).

There is no way dithering can't work, it's only black and white but in a diffusion pattern (attached is lower resolution to show the effect, the actual result will be hard to tell from grey scale... well hopefully not in your case).


dindunuffin

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Re: no success etching in greyscale
« Reply #22 on: May 22, 2016, 03:01:11 PM »
In all seriousness, what I'm gathering is that there is something in my current driver that is not responding to the power level commands?  Am I understanding this correctly?

Is there a replacement laser current driver module thingy?   And where is it on the laser body? under the fan?
If I can find it, I will compare it to the picture of yours that you've posted above.

I'll try that dithering file you posted as well. 

There was another conversation regard the L5 board that may have been this same issue, but due to my lack of technical knowledge I had no answer.

Quote
I have the L5 Board too. My Machine is the 1.6W A5 from Banggood.
I've tested it the last 2 Days, but i still have some problems with the Laser power. Unlike the L1 and L2 board the L5 doesn't have a variable Laserpower module in the lower left corner. Instead it seems to be a thyristor or something like that (will add a picture later). Also there is no jumper for the Laser voltage and instead of the capacitor there is a potentiometer.

I've installed the J-Tech Grbl version yesterday and tested the PWM Lasercontrol. The problem now is as follows: With the Laserpower under 200 (<M03 S200) the Laser turns on, but it isn't burning anything. There is no noticable difference between S50 and S190 for example. But as soon as the Laserpower is over 200 it runs on full power. Also there is no difference between 200 and 255.

« Last Edit: May 22, 2016, 03:10:30 PM by dindunuffin »

Zax

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Re: no success etching in greyscale
« Reply #23 on: May 22, 2016, 03:16:02 PM »
That was the reason I tested an L1, L2 and L5 board to see if they made a difference.

Since it didn't, I can only guess that the constant current driver (under the fan) doesn't switch on quick enough to support PWM.

Using an external current driver for the diode which has TTL switching built in seems like the simple solution, unless of course we can get these to support an input signal. I really need to pull the board out and do some investigation.

http://benboxlaser.us/index.php?topic=206.msg2520#msg2520

dindunuffin

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Re: no success etching in greyscale
« Reply #24 on: May 22, 2016, 07:16:02 PM »
I will order the current driver board, and since I have another L6? board already ordered, I should have enough parts to at least experiment. 

I will also see if I can take a look at my laser board and post a picture.

caperry88

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Re: no success etching in greyscale
« Reply #25 on: May 23, 2016, 03:53:01 AM »
Sorry for being so late to the conversation, but have you changed your resolution at all during your testing?  Also, did you change your max speed within the GRBL?  I found my was extremely low right off so varying my speeds did nothing for me because my limit was set at like 200.


check $100 and $110 for your max rate.
 
Equipment:  Gearbest 2500mw A5 Mini Laser Engraving Machine  -  2500MW  SILVER 167912906 Air-cooling Weak Light Automatic Positioning DIY Kit
Software: T2Laser with J-Tech Photonics 0.9g Grbl

Zax

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Re: no success etching in greyscale
« Reply #26 on: May 23, 2016, 04:47:29 AM »
check $100 and $110 for your max rate.

I think you mean $110 and $111

T2Laser defaults are 3000 which should be OK for most systems. I do have low acceleration values of 200 which you can increase but at higher values and high speed you could see backlash issues with the scanning (causing jagged edges).

dindunuffin

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Re: no success etching in greyscale
« Reply #27 on: May 23, 2016, 06:32:31 PM »
For $110 & $111 they are set at 3000.

Zax, you stated
Quote
So I did notice that the constant current driver has a T+/T- input, so wondering if that's for TTL.
What is TTL and how does that impact the current limitations?

And you stated
Quote
Using an external current driver for the diode which has TTL switching built in seems like the simple solution
Is this a replacement board or will I need to do some modification work?

One more question.  Do you need to dither an image before you import it into T2laser, or just take any image and click the dither button?  Just want to make sure I'm removing any user error from the situation. 
« Last Edit: May 23, 2016, 06:35:09 PM by dindunuffin »

Zax

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Re: no success etching in greyscale
« Reply #28 on: May 23, 2016, 07:09:58 PM »
TTL (5V logic) just means you can control the laser on/off with a separate signal rather than switching the actual input voltage.

It would require some re-wiring but nothing too significant.

You just load the image and make sure dither mode is selected.

dindunuffin

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Re: no success etching in greyscale
« Reply #29 on: May 23, 2016, 07:24:09 PM »
I just ran the dithered test image you provided and it worked quite well.  I will keep experimenting and testing until I figure out how to get better results from some other images.